fib_dxr: code hygiene, prune old code, no functional changes

The !DXR2 code corresponds to the original DXR encoding proposal from
2012 with a single direct-lookup stage, which is inferior to the more
recent (DXR2) variant with two-stage trie both in terms of memory
footprint of the lookup structures, and in terms of overall lookup
througput.

I'm axing the old code chunks to (hopefully) somewhat improve readability,
as well as to simplify future maintenance and updates.

MFC after:	1 week

sys/netinet/in_fib_dxr.c

@@ -1,7 +1,7 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
- * Copyright (c) 2012-2022 Marko Zec
+ * Copyright (c) 2012-2024 Marko Zec
  * Copyright (c) 2005, 2018 University of Zagreb
  * Copyright (c) 2005 International Computer Science Institute
  *
@@ -68,9 +68,6 @@
 
 CTASSERT(DXR_TRIE_BITS >= 16 && DXR_TRIE_BITS <= 24);
 
-/* DXR2: two-stage primary trie, instead of a single direct lookup table */
-#define	DXR2
-
 #if DXR_TRIE_BITS > 16
 #define	DXR_D			16
 #else
@@ -317,7 +314,6 @@ range_lookup(struct range_entry_long *rt, struct direct_entry de, uint32_t dst)
 		    ntohl(key.addr4.s_addr))]);				\
 	}
 
-#ifdef DXR2
 #if DXR_TRIE_BITS > 16
 DXR_LOOKUP_DEFINE(16)
 #endif
@@ -328,23 +324,16 @@ DXR_LOOKUP_DEFINE(12)
 DXR_LOOKUP_DEFINE(11)
 DXR_LOOKUP_DEFINE(10)
 DXR_LOOKUP_DEFINE(9)
-#endif /* DXR2 */
 
 static int inline
 dxr_lookup(struct dxr *dxr, uint32_t dst)
 {
 	struct direct_entry de;
-#ifdef DXR2
 	uint16_t *dt = dxr->d;
 	struct direct_entry *xt = dxr->x;
 
 	de = xt[(dt[dst >> dxr->d_shift] << dxr->x_shift) +
 	    ((dst >> DXR_RANGE_SHIFT) & dxr->x_mask)];
-#else /* !DXR2 */
-	struct direct_entry *dt = dxr->d;
-
-	de = dt[dst >> DXR_RANGE_SHIFT];
-#endif /* !DXR2 */
 	if (__predict_true(de.fragments == FRAGS_MARK_HIT))
 		return (de.base);
 	return (range_lookup(dxr->r, de, dst));
@@ -571,7 +560,6 @@ chunk_unref(struct dxr_aux *da, uint32_t chunk)
 	LIST_INSERT_HEAD(&da->unused_chunks[i], cdp, cd_hash_le);
 }
 
-#ifdef DXR2
 static uint32_t
 trie_hash(struct dxr_aux *da, uint32_t dxr_x, uint32_t index)
 {
@@ -670,7 +658,6 @@ trie_unref(struct dxr_aux *da, uint32_t index)
 			}
 	} while (tp != NULL);
 }
-#endif
 
 static void
 heap_inject(struct dxr_aux *da, uint32_t start, uint32_t end, uint32_t preflen,
@@ -864,12 +851,10 @@ dxr_build(struct dxr *dxr)
 	uint32_t r_size, dxr_tot_size;
 	uint32_t i, m, range_rebuild = 0;
 	uint32_t range_frag;
-#ifdef DXR2
 	struct trie_desc *tp;
 	uint32_t d_tbl_size, dxr_x, d_size, x_size;
 	uint32_t ti, trie_rebuild = 0, prev_size = 0;
 	uint32_t trie_frag;
-#endif
 
 	MPASS(dxr->d == NULL);
 
@@ -907,7 +892,6 @@ dxr_build(struct dxr *dxr)
 		}
 		range_rebuild = 1;
 	}
-#ifdef DXR2
 	if (da->x_tbl == NULL) {
 		da->x_tbl = malloc(sizeof(*da->x_tbl) * da->xtbl_size,
 		    M_DXRAUX, M_NOWAIT);
@@ -918,7 +902,6 @@ dxr_build(struct dxr *dxr)
 		}
 		trie_rebuild = 1;
 	}
-#endif
 
 	microuptime(&t0);
 
@@ -970,7 +953,6 @@ range_build:
 	r_size = sizeof(*da->range_tbl) * da->rtbl_top;
 	microuptime(&t1);
 
-#ifdef DXR2
 	if (range_rebuild ||
 	    abs(fls(da->prefixes) - fls(da->trie_rebuilt_prefixes)) > 1)
 		trie_rebuild = 1;
@@ -1044,10 +1026,6 @@ dxr2_try_squeeze:
 		goto dxr2_try_squeeze;
 	}
 	microuptime(&t2);
-#else /* !DXR2 */
-	dxr_tot_size = sizeof(da->direct_tbl) + r_size;
-	t2 = t1;
-#endif
 
 	dxr->d = malloc(dxr_tot_size, M_DXRLPM, M_NOWAIT);
 	if (dxr->d == NULL) {
@@ -1055,7 +1033,6 @@ dxr2_try_squeeze:
 		    "Unable to allocate DXR lookup table");
 		return;
 	}
-#ifdef DXR2
 	memcpy(dxr->d, da->d_tbl, d_size);
 	dxr->x = ((char *) dxr->d) + d_size;
 	memcpy(dxr->x, da->x_tbl, x_size);
@@ -1063,10 +1040,6 @@ dxr2_try_squeeze:
 	dxr->d_shift = 32 - da->d_bits;
 	dxr->x_shift = dxr_x;
 	dxr->x_mask = 0xffffffffU >> (32 - dxr_x);
-#else /* !DXR2 */
-	memcpy(dxr->d, da->direct_tbl, sizeof(da->direct_tbl));
-	dxr->r = ((char *) dxr->d) + sizeof(da->direct_tbl);
-#endif
 	memcpy(dxr->r, da->range_tbl, r_size);
 
 	if (da->updates_low <= da->updates_high)
@@ -1076,36 +1049,24 @@ dxr2_try_squeeze:
 	da->updates_high = 0;
 	microuptime(&t3);
 
-#ifdef DXR2
 	FIB_PRINTF(LOG_INFO, da->fd, "D%dX%dR, %d prefixes, %d nhops (max)",
 	    da->d_bits, dxr_x, rinfo.num_prefixes, rinfo.num_nhops);
-#else
-	FIB_PRINTF(LOG_INFO, da->fd, "D%dR, %d prefixes, %d nhops (max)",
-	    DXR_D, rinfo.num_prefixes, rinfo.num_nhops);
-#endif
 	i = dxr_tot_size * 100;
 	if (rinfo.num_prefixes)
 		i /= rinfo.num_prefixes;
 	FIB_PRINTF(LOG_INFO, da->fd, "%d.%02d KBytes, %d.%02d Bytes/prefix",
 	    dxr_tot_size / 1024, dxr_tot_size * 100 / 1024 % 100,
 	    i / 100, i % 100);
-#ifdef DXR2
 	FIB_PRINTF(LOG_INFO, da->fd,
 	    "%d.%02d%% trie, %d.%02d%% range fragmentation",
 	    trie_frag / 100, trie_frag % 100,
 	    range_frag / 100, range_frag % 100);
-#else
-	FIB_PRINTF(LOG_INFO, da->fd, "%d.%01d%% range fragmentation",
-	    range_frag / 100, range_frag % 100);
-#endif
 	i = (t1.tv_sec - t0.tv_sec) * 1000000 + t1.tv_usec - t0.tv_usec;
 	FIB_PRINTF(LOG_INFO, da->fd, "range table %s in %u.%03u ms",
 	    range_rebuild ? "rebuilt" : "updated", i / 1000, i % 1000);
-#ifdef DXR2
 	i = (t2.tv_sec - t1.tv_sec) * 1000000 + t2.tv_usec - t1.tv_usec;
 	FIB_PRINTF(LOG_INFO, da->fd, "trie %s in %u.%03u ms",
 	    trie_rebuild ? "rebuilt" : "updated", i / 1000, i % 1000);
-#endif
 	i = (t3.tv_sec - t2.tv_sec) * 1000000 + t3.tv_usec - t2.tv_usec;
 	FIB_PRINTF(LOG_INFO, da->fd, "snapshot forked in %u.%03u ms",
 	    i / 1000, i % 1000);
@@ -1194,7 +1155,6 @@ static void *
 choose_lookup_fn(struct dxr_aux *da)
 {
 
-#ifdef DXR2
 	switch (da->d_bits) {
 #if DXR_TRIE_BITS > 16
 	case 16:
@@ -1215,7 +1175,6 @@ choose_lookup_fn(struct dxr_aux *da)
 	case 9:
 		return (dxr_fib_lookup_9);
 	}
-#endif /* DXR2 */
 	return (dxr_fib_lookup);
 }